Wideband double-element ring slot antenna - Electronics Letters

Introduction: Annular ring slot antennas are considered to be among the narrowband resonant antennas and occupy an area of l=4p at their first resonance [1]. Multi-element concentric ring slots have been used to design multi-band antennas [2]. However, because of transmission zeros that exist between the different resonances, these resonances cannot easily be merged to obtain a wideband response. In this Letter, we present a new way of feeding the double-element ring antenna to remove this transmission zero and obtain a wideband antenna. It is shown that the new antenna has a bandwidth of 36% which is about six times that of the bandwidth of each antenna alone. This increase in the bandwidth is obtained without putting any constraints on radiation patterns, antenna efficiency (gain), or adversely affecting the antenna polarisation purity.